#define MOD_TYPE 1 #include using namespace std; #include //#include //#include //#include using namespace atcoder; #if 0 #include #include using Int = boost::multiprecision::cpp_int; using lld = boost::multiprecision::cpp_dec_float_100; #endif #if 1 #include #include #include #include using namespace __gnu_pbds; using namespace __gnu_cxx; template using extset = tree, rb_tree_tag, tree_order_statistics_node_update>; #endif #if 0 #pragma GCC target("avx2") #pragma GCC optimize("O3") #pragma GCC optimize("unroll-loops") #endif #pragma region Macros using ll = long long int; using ld = long double; using pii = pair; using pll = pair; using pld = pair; template using smaller_queue = priority_queue, greater>; #if MOD_TYPE == 1 constexpr ll MOD = ll(1e9 + 7); #else #if MOD_TYPE == 2 constexpr ll MOD = 998244353; #else constexpr ll MOD = 1000003; #endif #endif using mint = static_modint; constexpr int INF = (int)1e9 + 10; constexpr ll LINF = (ll)4e18; constexpr double PI = acos(-1.0); constexpr double EPS = 1e-11; constexpr int Dx[] = {0, 0, -1, 1, -1, 1, -1, 1, 0}; constexpr int Dy[] = {1, -1, 0, 0, -1, -1, 1, 1, 0}; #define REP(i, m, n) for (ll i = m; i < (ll)(n); ++i) #define rep(i, n) REP(i, 0, n) #define REPI(i, m, n) for (int i = m; i < (int)(n); ++i) #define repi(i, n) REPI(i, 0, n) #define YES(n) cout << ((n) ? "YES" : "NO") << "\n" #define Yes(n) cout << ((n) ? "Yes" : "No") << "\n" #define possible(n) cout << ((n) ? "possible" : "impossible") << "\n" #define Possible(n) cout << ((n) ? "Possible" : "Impossible") << "\n" #define all(v) v.begin(), v.end() #define NP(v) next_permutation(all(v)) #define dbg(x) cerr << #x << ":" << x << "\n"; #define UNIQUE(v) v.erase(unique(all(v)), v.end()) struct io_init { io_init() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << setprecision(30) << setiosflags(ios::fixed); }; } io_init; template inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; } template inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; } inline ll CEIL(ll a, ll b) { return (a + b - 1) / b; } template inline void Fill(A (&array)[N], const T &val) { fill((T *)array, (T *)(array + N), val); } template vector compress(vector &v) { vector val = v; sort(all(val)), val.erase(unique(all(val)), val.end()); for (auto &&vi : v) vi = lower_bound(all(val), vi) - val.begin(); return val; } template constexpr istream &operator>>(istream &is, pair &p) noexcept { is >> p.first >> p.second; return is; } template constexpr ostream &operator<<(ostream &os, pair p) noexcept { os << p.first << " " << p.second; return os; } ostream &operator<<(ostream &os, mint m) { os << m.val(); return os; } ostream &operator<<(ostream &os, modint m) { os << m.val(); return os; } template constexpr istream &operator>>(istream &is, vector &v) noexcept { for (int i = 0; i < v.size(); i++) is >> v[i]; return is; } template constexpr ostream &operator<<(ostream &os, vector &v) noexcept { for (int i = 0; i < v.size(); i++) os << v[i] << (i + 1 == v.size() ? "" : " "); return os; } random_device seed_gen; mt19937_64 engine(seed_gen()); struct BiCoef { vector fact_, inv_, finv_; BiCoef(int n) noexcept : fact_(n, 1), inv_(n, 1), finv_(n, 1) { fact_.assign(n, 1), inv_.assign(n, 1), finv_.assign(n, 1); for (int i = 2; i < n; i++) { fact_[i] = fact_[i - 1] * i; inv_[i] = -inv_[MOD % i] * (MOD / i); finv_[i] = finv_[i - 1] * inv_[i]; } } mint C(ll n, ll k) const noexcept { if (n < k || n < 0 || k < 0) return 0; return fact_[n] * finv_[k] * finv_[n - k]; } mint P(ll n, ll k) const noexcept { return C(n, k) * fact_[k]; } mint H(ll n, ll k) const noexcept { return C(n + k - 1, k); } mint Ch1(ll n, ll k) const noexcept { if (n < 0 || k < 0) return 0; mint res = 0; for (int i = 0; i < n; i++) res += C(n, i) * mint(n - i).pow(k) * (i & 1 ? -1 : 1); return res; } mint fact(ll n) const noexcept { if (n < 0) return 0; return fact_[n]; } mint inv(ll n) const noexcept { if (n < 0) return 0; return inv_[n]; } mint finv(ll n) const noexcept { if (n < 0) return 0; return finv_[n]; } }; BiCoef bc(1000010); #pragma endregion // ------------------------------- struct SCC { int V; vector> G, Gr; vector comp, order, used; SCC(int V_) : V(V_), G(V_), Gr(V_), comp(V_, -1), used(V_) {} void add_edge(int a, int b) { G[a].emplace_back(b); Gr[b].emplace_back(a); } // 番号はトポロジカル順 int operator[](int k) { return comp[k]; } void dfs(int idx) { if (used[idx]) return; used[idx] = true; for (int to : G[idx]) dfs(to); order.emplace_back(idx); } void rdfs(int idx, int cnt) { if (comp[idx] != -1) return; comp[idx] = cnt; for (int to : Gr[idx]) rdfs(to, cnt); } // del_mul が false の場合高速になるが多重辺が生える vector> build(bool del_mul = true) { vector> res; for (int i = 0; i < G.size(); i++) dfs(i); reverse(begin(order), end(order)); int ptr = 0; for (int i : order) if (comp[i] == -1) rdfs(i, ptr), ptr++; res.resize(ptr); for (int i = 0; i < G.size(); i++) { for (auto &to : G[i]) { int x = comp[i], y = comp[to]; if (x == y) continue; res[x].push_back(y); } } if (del_mul) { for (auto &&v : res) { sort(begin(v), end(v)); auto itr = unique(begin(v), end(v)); v.erase(itr, v.end()); } } return res; } }; void solve() { int n, m; cin >> n >> m; SCC G(n); rep(i, m) { int a, b; cin >> a >> b; a--, b--; G.add_edge(a, b); } auto E = G.build(); n = E.size(); if (n == 1) { cout << 0 << "\n"; return; } vector in(n, 0), out(n, 0); rep(i, n) { for (auto j : E[i]) { in[i]++, out[j]++; } } int x = 0, y = 0; rep(i, n) { if (in[i] == 0) x++; if (out[i] == 0) y++; } cout << max(x, y) << "\n"; } int main() { solve(); }